The present invention relates to a method of producing granules containing peroxy compounds and the granules obtainable in this manner. The present invention further relates to the use of these granules as a bleaching agent or bleaching agent component, in particular to the use thereof in particulate or liquid detergents and cleaning agents, and to the production thereof.
The particulate bleaching components conventionally used hitherto in detergents, such as for example alkali metal perborates or percarbonates, are highly moisture-sensitive, that is to say they often lose their bleaching action within a short time due to a loss of active oxygen, since even solid detergents and cleaning agents always have a certain water content or water penetration from the air is inevitable during storage thereof, if the bleaching agent component is not protected against moisture, for example by the application of a coating layer.
Peroxycarboxylic acids, in particular imidoperoxycarboxylic acids, the most important representative of which is phthalimidoperoxycaproic acid (PAP), are likewise known as bleaching components for detergents and cleaning agents; although these are less sensitive to hydrolysis than the stated inorganic compounds, their storage stability is insufficient to ensure long-term usability of the corresponding detergent or cleaning agent without an accompanying loss of activity.
Because of the disadvantages which arise in relation to a change in the detergent or cleaning agent formulation as a result of the degradation of the bleaching agent component such as imidoperoxycarboxylic acid, in particular PAP, it has been attempted in the prior art to encapsulate the imidoperoxycarboxylic acids (e.g. PAP) effectively, such that they cannot come into contact with the other components of the detergent or cleaning agent formulation.
For instance, European patent EP 0 510 761 B1 describes a method of encapsulating detergent additives in general, such as for example enzymes, bleaching activators, bleaching catalysts and bleaching agents, also including PAP, a wax being used as a protective coating for encapsulation, the melting point of which is between 40° C. and 50° C. The wax-coated particles are in this case produced by spraying on the molten wax. In this case, the wax has initially to be heated to temperatures above its melting point, which may be a disadvantage with regard to thermally sensitive substances requiring encapsulation. This method has the additional disadvantage that the active substance is only released at temperatures above the melting point of the wax used, i.e. only above temperatures of between 40° C. and 50° C., which in particular does not meet current consumer or user requirements, since, in the light of the development of more efficient detergent and cleaning agent formulations and savings in energy costs, it is frequently desired to carry out washing at even lower temperatures, in particular at around 30° C. Furthermore, a wax with a high melting point has the disadvantage that it causes residues to remain on laundry, in particular at low temperatures, since it is not fully emulsified at such temperatures.
European patent EP 0 653 485 B1 relates to active ingredient-containing capsule compositions, which may contain bleaching agents such as for example PAP and in which the active ingredient is present inside the capsule as a dispersion in oil. The production of these capsules, whose shell is formed of hydrophilic polymers which only become soluble during the washing process or use, requires a complex emulsifying process which is technologically not straightforward to perform.
Bleaching agent granules are known from European patent application EP 0 816 481 A2 which contain a peracid such as for example PAP and an agglomeration aid in the ratio by weight of 1:2 to 1:50 and citric acid monohydrate as the exotherm control active ingredient. European patent EP 0 695 343 B1 relates to amidoperoxycarboxylic acid particles, which have been spray-coated in a fluidized bed with a coating of water-soluble salt and contain less than 2 wt. % water.